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Full text of "Metalworking"

College Bike Trunk 



i 



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College Bike Trunk 

Written By: Frank Yost 



f TOOLS: 

Bending brake (1) 
C-clamp (a couple) 
Center punch (1) 
Combination square (1) 
Dremel rotary tool (1) 
Drill (1) 
Hammer (1) 
Marker (1) 
Metal files (1) 
Pliers (1) 
Pop rivet tool (1) 
Sandpaper (1) 
Scissors (1) 
Tinsnips (1) 
Wax paper ( 1 ) 
Wood blocks (1) 
X-Acto knifed) 



© PARTS: 



Steel sheet (2) 

Aluminum sheet (1) 
/ used an old stop sign. 

Metal sheet (1) 
optional 

Pop rivets (100) 

Include matching backup washers 

matching backup washers 

Pop rivets (10) 

Include matching backup washers 

Piano hinge (1) 

Inner tube (1) 
for bike tire, used 

Brass knob (1) 

Draw hasps (2) 

Pipe hanging clips (4) 

Bolts (5) 

Taped) 

Bike rack (1) 

/ used a 27770cm rack 



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College Bike Trunk 



Rear reflector (1) 

Glazing and spot putty (1) 
from an auto parts store 

Silicone glue (1) 

Craft glued) 

Don't use cyanoacrylate (crazy/super) 

glue. 

Spray paint (1) 

You need a white primer, flat black, and 

flat white 

Padlocks (2) 



SUMMARY 

Growing up, I would often visit my grandparents in Dinkytown, the southeast Minneapolis 
neighborhood near the University of Minnesota that was named after the freshman cap worn 
there a century ago. I remember seeing students on ten-speeds carrying their stuff in milk 
crates that they strapped to the rear rack with bungee cords. 

Inspired by that image, I wanted something better and more secure. Car drivers can lock 
things up while running errands, so why should cyclists have to carry everything around with 
them? 

So I designed this sheet metal bike trunk. I sized it to hold two 1 -gallon jugs of milk with a 
little room to spare. Its top angles away from the seat like a saddle does, so nothing rubs 
against the rider. And its 2 latches will accept 2 padlocks to secure the contents against 
casual theft. 

NOTE: If you like, you can prototype the project in cardboard before going to metal. For 
more advice on working with sheet metal, see my Retro Racer project ( MAKE Volume 11 . 
page 97) and Mister Jalopy's "Q&D: Holes, Rivets, and Bent Metal" ( MAKE Volume 05 . page 
110). 



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College Bike Trunk 





• Download the project templates 
from the Files section above 
(PDFs), and print them at full size. 
Cut them out, and tape them onto 
the sheet metal using double-sided 
tape, or else cut holes in the 
templates and stick masking tape 
over the holes. 

• Trace around the edge of each 
template with a fine permanent 
marker, and use tinsnips to cut out 
pieces A1/A2, B1, C1/C2, and D1. 
Don't cut apart A1 and A2 or C1 
and C2 yet. After cutting, pound flat 
any uneven edges with a hammer 
and wood block, and file smooth 
the sharp edges. 

• I used shiny aluminum for the 
"chrome" tail ornament E1, but 
stainless would also work. I've 
found that aluminum doesn't pound 
back flat well, so I cut it out with a 
Dremel and cutting wheel. 

• For the base piece (not shown on 
the templates) cut a 14"x7 1 /4 n 
rectangle out of thicker aluminum. 

• Drill 1/8" holes around the 
perimeter of body piece A1/A2 as 
shown on the template. For the 8 
oval cutouts in E1, drill holes inside 
each, then work the shapes out 
with a file. 



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College Bike Trunk 





Cut the inner tube lengthwise, wash 
it thoroughly with soap and water, 
and let it dry overnight. 

Lay the trunk lip piece D1 on wax 
paper, then coat it with E-6000 
glue. Cover it fully with flat pieces 
of inner tube, then more wax paper. 
Clamp it all flat using C-clamps and 
scrap plywood. 

Let the glue dry for 3 days or more, 
then remove the clamps and wood, 
and peel off the wax paper. Trim 
any excess rubber around the 
edges of the metal with an X-Acto 
knife. 







Using the sheet metal brake, bend down the 2 middle lines of piece A1/A2 at 42°, then 
bend the bottom tabs inward at 90°. 

Similarly bend B1, C1/C2, D1, and E1 along the lines indicated on the templates. 

• NOTE: Front cap B1 and end cap C1/C2 look very similar; don't mix them up. 




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College Bike Trunk 




Temporarily assemble end caps B1 and C1/C2 to the body A1/A2, clamping them together 
at the bottom. Fit them at the top and re-drill through one 1/8" hole on each bend plane in 
A1/A2. Pop-rivet through these holes to hold the pieces in place temporarily, then drill 
through all the remaining holes. 

Drill out the pop-rivets using the same 1/8" bit, pull everything apart, and file down any 
burrs. 





\ 





• Now that everything lines up, put it back together again. Glob the Dynatron putty on the 
tabs of B1 and C1/C2 and rivet the pieces to A1/A2 through all the holes. 

• Wipe the excess putty with a rag and let it dry. 



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College Bike Trunk 







Cut templates A1/A2 and C1/C2 apart as indicated, tape them in place on the trunk, and 
trace them with a marker. Then use a Dremel tool to cut out the door A2 and the hinge joint 
between C1 and C2. 

Cut a Vi" gap between C1 and C2 for the hinge, then clamp on the hinge, mark and drill 
through its mounting holes, and pop-rivet it in place. 

Use a Dremel to widen the gap between door A2 and trunk A1 to 1/8". 

Bend the trunk lip D1 to fit inside A1 , level or angled just slightly downward. Clamp it in 
place, then drill and rivet in place, backing the rivets with washers. 





• Drill the tabs around the underside 
of the trunk with 1/8" holes 1" 
apart. Fit the trunk over the base, 
then mark and drill matching holes 
in the aluminum. 

• Put a bead of silicone glue between 
the panels over the holes, and rivet 
the base in place. 

• Wipe excess silicone with a rag 
and let dry. 



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College Bike Trunk 







Place the 2 hasps, one on each side. Mark and drill through the mounting holes, then rivet 
the hasps in place using the larger, 3/16" bit and rivets, reinforced with washers. 

Drill a hole for the brass knob on top of the door. For decorative tailpiece E1 , position it on 
the door and mark and drill 1/8" holes in both pieces, but don't rivet it on yet. 







• Fit the 5/16" pipe clips around the tubing on either side of your bike rack's platform. Flip 
the trunk upside down and center the rack on the base. 

• Mark the clip mounting hole positions and drill 4 corresponding 1/4" holes in the base, plus 
an extra hole centered in back where the rack already has a hole. 



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College Bike Trunk 



Step 10 — Paint and finish. 




• Paint the inside of the trunk flat black. 

• Sand down the putty on the exterior, then paint it with primer and white paint (to keep cool 
in the sun). 

• I cut "College Bike Trunk" emblems out of black tape and stuck them to the sides. 

• Finally, pop-rivet the tail on, and stick the red reflector on the back. 



Step 11 — Install and celebrate. 





Install your new bike trunk on the rack using the 1/4-20 bolts. 

To lock the trunk, use padlocks with shackles IV2" long, one on each latch. 

Now you're done. It's time to celebrate like a college student — go to the store, and pick 
up some beer! 



This project first appeared in MAKE Volume 23 , page 135. 



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